并联碳化硅MOSFET短路振荡机理

Short-circuit Oscillation Mechanism of Parallel SiC MOSFET

碳化硅(SiC)金属氧化物半导体场效应晶体管(MOSFET)为高性能电力电子技术提供了技术保障,其短路承受能力是进一步提升电力电子变换器可靠性的关键;特别是在大功率场合,经常将SiC MOSFET并联使用,然而影响并联SiC器件短路振荡的关键因素并不十分明确,振荡机理有待进一步研究。此处以并联SiC MOSFET为研究对象,建立在短路工况下的等效数学模型,分析影响并联短路特性的关键因素并进行实验验证,归纳短路振荡机理。理论分析与实验结果表明,当并联SiC MOSFET发生短路故障时,栅极驱动电阻和功率回路杂散电感是导致器件并联系统振荡的主要因素,过小的栅极驱动电阻使得并联系统振荡频率和尖峰增大;过大的功率回路杂散电感导致系统振荡频率降低,而振荡尖峰增大,系统的剧烈振荡不利于SiC MOSFET稳定性提高。

The application of silicon carbide(SiC)metal oxide semiconductor field effect transistor(MOSFET)provides technical support for the field of high-performance power electronics technology,and their short-circuit tolerance has attracted much attention,which is the key to further improving the reliability of power electronic converters.Especially in the occasion of high-power conversion,it is common that SiC MOSFET will be used in parllel.However,the key factors affecting short-circuit oscillations in parallel SiC devices are not well understood and the oscillation mechanism needs further study.Therefore,parallel SiC MOSFET as the research object is taken,the equivalent mathematical mod-el of the parallel devices is established under short-circuit conditions,the key factors affecting the short-circuit cha-acteristics are analyzed of parallel SiC MOSFET,and experimental verification is carried out.Theoretical analysis and experimental results show that when a paralleled SiC MOSFET short-circuit fault occurs,a too-small gate driving re-sistance and too-large stray inductance of the power loop are the main factors leading to the oscillation of the paral-lel system.A too-small gate driving resistance increases the oscillation frequency of the drain voltage and gate-source voltage and increases the oscillation peak.A too-large stray inductance of the power loop leads to the decrease of os-cillation frequency and the increase of oscillation peak.The violent oscillation of the system is not conducive to the stability improvement of SiC MOSFET.